铁素体/马氏体钢在超临界水环境氧化后形成均匀完整的氧化膜，但氧化增重曲线偏离抛物线规律，发现氧化膜中含有大量的微孔洞，其数量和尺寸随溶解氧量和氧化时间变化。超临界水高扩散系数、低运动粘度、分子平均自由程小等特点，使得水分子在氧化膜微孔洞中微观扩散机制由努森扩散转化为体扩散，扩散速率明显增加。氧化膜微孔洞变化规律和超临界水在微孔洞中的扩散机制对氧化动力学研究具有重要意义。选择P92钢在不同溶解氧超临界水环境中进行氧化试验，研究微孔洞特征随溶解氧和氧化时间的变化规律及溶解氧对其影响机理。引入多孔介质理论，建立氧化膜的多孔介质模型，研究超临界水分子在氧化膜多孔介质中的微观扩散机制，推导水分子扩散系数的数学表达。综合氧化膜固体中的扩散系数和孔洞中的扩散系数，提出新的氧化动力学模型。

A uniform and integrated oxide scale is formed on the ferritic-martensitic steel after exposing to the supercritical water. The curves of the weight gain are deviated from the parabolic law. Amounts of pores of which the number and diameter change with the dissolved oxygen and exposure time is observed in the oxide scale. The properties of supercritical water including the high diffusion coefficient, the low kinematic viscosity and the small mean free path change the diffusion mechanism of water molecular from Knudsen diffusion to bulk diffusion, thus a obvious increasing of diffusion velocity. The change law of the micro-pores and the diffusion mechanism of supercritical water through the micro-channel of oxide scale have a distinct influence on the oxidation kinetics. A series of experiments of P92 steel is tested in supercritical water with different dissolved oxygen. The characteristics of the pores are detected. The rule of the pore changing with the dissolved oxygen and exposure time and the influence mechanism of dissolved oxygen on the pores are investigated. Based on the theory of porous media, the porous media model of the oxide scale will be established , the diffusion mechanism of supercritical water molecules in the oxide scale porous media will be investigated, therefore, the mathematical expression of the diffusion coefficient will be deduced. Combining the diffusion coefficient in solid oxide with the one in the pores, a new oxidation dynamics model will be obtained.